Recent file thumbnail sizes

You could always make a new topic marked as an idea rather than as a discussion for a feature request.

https://community.adobe.com/t5/photoshop-ecosystem-ideas/how-do-i-write-a-feature-request/idi-p/12384447

Perhaps Adobe will add this when they add the ability to remove thumbnails.  :]

I don't see a way to change thumbnail sizes on the Home screen unless you want to try List View.

Bridge would be a better option to adjust thumbnail size to taste. It has a Recent Files view  Bridge is free of charge for Creative Cloud subscribers.